1. Introduction to Types of Chemical Reactions

2. I can identify elements vs. compounds in a chemical equation
Objective
I can identify elements vs. compounds in a chemical equation
I can name the 7 diatomic elements
I can identify precipitation vs. redox reactions

3. Review: Compounds vs. Elements
Compounds are combinations of elements that are chemically combined.
examples: H2O2 CO2 H2O C4H8 Fe2O3
When not in a compound, most elements exist as single atoms but seven elements exist as diatomic molecules
There are 7 diatomic elements
H2, O2, F2, Br2, I2, N2, Cl2

4. H2, O2, F2, Br2, I2, N2, Cl2
there are 7 diatomic elements

5. Boron as B2 Carbon as C2 Oxygen as O2 Helium as He2
Which of the following would appear as a diatomic element in a chemical reaction?
Boron as B2
Carbon as C2
Oxygen as O2
Helium as He2
[Default]
[MC Any]
[MC All]

6. Chemical Reactions
Every minute of the day chemical reactions take place.
In your body, complex chemical reactions digest food.
Plants use sunlight to drive the photosynthesis reaction.
A chemical reaction produces electrical energy in your car battery
An undesirable chemical reaction with oxygen occurs with your car fender to produce rust.

7. Describing Chemical Reactions
Describing chemical reactions using balanced chemical equations is an essential skill.
reactants → products
Symbols you might see in a balanced chemical equation:
(s) solid
(l) liquid
(g) gas
(aq) aqueous – dissolved in water
D (above the arrow) indicates the reactants are heated

8. Example
When solid sodium hydrogen carbonate is heated, it decomposes, forming the products solid sodium carbonate, carbon dioxide gas and water vapor.
Write the Chemical Equation:

9. What does the symbol (s) after Na(HCO3) stand for in this chemical equation?
solution
solid
substance
sodium
[Default]
[MC Any]
[MC All]

10. What does the symbol (g) after CO2 stand for in this chemical equation?
grams
group
gas
ground state
[Default]
[MC Any]
[MC All]

11. Two categories of Chemical Reactions
Chemical reactions can be categorized into two types;
Precipitation reactions.
Oxidation – Reduction reactions called redox
In a precipitation reaction, cations and anions in aqueous solution are rearranged to form a solid product called a precipitate.
In an oxidation – reduction reaction (or redox reaction), electrons are lost by one element and gained by another element.

12. Examples of Reactions Precipitate Reaction examples:
AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)
Na2S(aq) + Cd(NO3)2(aq) → CdS(s) + 2NaNO3(aq)
BaCl2(aq) + K2CO3(aq) → BaCO3(s) + 2KCl(aq)
Pb(ClO4)2(aq) + 2NaI(aq) → PbI2(s) + 2NaClO4(aq)
What do these reactions have in common?

13. Examples of Reactions Redox reaction examples:
2K(s) + Cl2(g) → 2KCl(s)
2H2O2(aq) → 2H2O(l) + O2(g)
2Al(s) + 3Cu(SO4)(aq) → 3Cu(s) + Al2(SO4)3(aq)
Pb(s) AgNO3(aq) → 2 Ag(s) + Pb(NO3)2(aq)
CH4(g) + O2(g) → CO2(g) + 2 H2O(l)
What do these reactions have in common?

14. Compare reactants cations & anions are rearranged
precipitation reactions
redox (oxidation-reduction) reactions
reactants cations & anions are rearranged
aqueous solutions react to form a precipitate
(aq) + (aq)  (s) + (aq)
a precipitate is a solid formed in a solution
reactants & products are ionic compounds – NOT elements
electrons are lost by one element and gained by another element
typically a reactant or product or both is an element
elements can be diatomic molecules
H2, O2, N2, F2, Br2, I2, Cl2
Compare

15. Identify as precipitation or redox reaction: H2(g) + F2(g) → 2 HF(g)
precipitaiton
redox
[Default]
[MC Any]
[MC All]

16. Identify as precipitation or redox reaction:
Identify as precipitation or redox reaction: 2Al(s) + 3Cu(SO4)(aq) → 3Cu(s) + Al2(SO4)3(aq)
precipitaiton
redox
[Default]
[MC Any]
[MC All]

17. Identify as precipitation or redox reaction: 2NaOH(aq) + MgCl2(aq) → Mg(OH)2(s) + 2NaCl(aq)
precipitaiton
redox
[Default]
[MC Any]
[MC All]

18. Identify as precipitation or redox reaction:
Identify as precipitation or redox reaction: C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(l)
precipitaiton
redox
[Default]
[MC Any]
[MC All]

19. Identify as precipitation or redox reaction: MgCl2(s) → Mg(s) + Cl2(g)
precipitaiton
redox
[Default]
[MC Any]
[MC All]

20. Identify as precipitation or redox reaction: Na2S(aq) + Cd(NO3)2(aq) → CdS(s) + 2NaNO3(aq)
[Default]
[MC Any]
[MC All]

21. Identify as precipitation or redox reaction: 2 Al(s) + 3 Cu(SO4)(aq) → 3 Cu(s) + Al2(SO4)3(aq)
[Default]
[MC Any]
[MC All]

22. I can identify elements vs. compounds in a chemical equation
Objective
I can identify elements vs. compounds in a chemical equation
I can name the 7 diatomic elements
I can identify precipitation vs. redox reactions